Abstract: To solve the continuous wave information demodulation problem of measurement while drilling (MWD), a kind of 2DPSK demodulation scheme for continuous wave was proposed. Analyzing the transmission characteristics of measurement system with drilling, a math model was established. According to the characteristics of measurement system, a series of continuous signal modulation techniques were analyzed and compared, showing the suitability of 2DPSK signal for continuous wave information modulation under well. Then, the types of the underground noise were analyzed and a digital filter algorithm was designed for the continuous wave information demodulation system. According to the above analysis, an implementation scheme of the 2DPSK demodulation system was determined and the continuous wave information demodulation was achieved with FPGA. The results show that the demodulation system can recover the initial data accurately in the white noise channel.